This invention relates generally to containers and, more particularly, to containers formed of flexible sheet materials.
Flexible containers formed of sheet materials have been used for several years and are now gaining ever wider acceptance for holding various air-perishable products, e.g., foodstuffs, etc. Prior art flexible, air-tight containers are commonly constructed of some plastic film, metal foil, or combinations thereof, in one or more plies and sealed alone one or more seams. Such containers are usually vacuumized after filling but prior to sealing so that the contents of the container are not exposed to the degradation effects of air. Accordingly, products held in such containers can have a shelf life comparable to rigid containers, such as jars with screw-on lids or metal cans.
The advantages of flexible containers over rigid containers are many. For example, flexible containers can be manufactured at substantially lower cost and can be stored flat, thereby resulting in enormous space savings over rigid containers. Moreover, flexible containers are substantially lighter in weight, thereby resulting in reduced transportation costs for unfilled containers. Further still, flexible containers are generally of an overall parallelopiped shape when filled so that such containers take up considerably less shelf or storage space. Needless to say, this feature is of considerable importance insofar as transportation, storage, and display are concerned.
While prior art air-tight, flexible containers exhibit the aforementioned advantages over rigid containers, they still have not proved a completely acceptable alternative to hard containers for the air-tight storage of materials, particularly when it is desired to be able to open and reclose the container after its initial opening. In this regard, the seams of prior art flexible containers are usually permanent in the interest of air tightness and structural integrity and are commonly formed by conventional heat sealing or welding techniques. Thus, the prior art flexible container is opened by cutting or tearing one or more of its seams. Owing to the permanent nature of the sealed seams, the tearing of any seam to gain access to the contents of the container not only destroys the seal but frequently results in the tearing of the material of the container contiguous with the seam. This is an obviously undesirable result since it may render the container useless for reclosure and continued holding of the contents of the container. If the container is opened by cutting off its top below the heat seal line, while the wall portions forming the container are not torn (thus permitting reclosure), the container is nevertheless shorter and thus of lower volumetric capacity.
Various flexible packaging structures have been disclosed in the prior art utilizing tear strips and/or tear lines to facilitate opening of the container. Examples of such patents are U.S. Pat. Nos. 3,186,628 (Rohde), 3,535,409 (Rohde), and 3,939,972 (Mayworm).
In the U.S. Pat. No. Re. 30,726 (Otten et al.), there is disclosed a pouch composed of an extruded polymer film formed by a blend of polyethylene resin and an ionomer.
The pouch is formed by extruding the polyethylene/ionomer blend into a continuous tubular film which exhibits a linear tear property in the machine direction. By linear tear property, it is meant that the material has the inherent property to tear readily by hand along the substantially straight line by a normal shearing or parting motion without the need for guiding the tear. The tubular film is then slit longitudinally, cut into transverse sections, and heat sealed adjacent the transverse cuts to form a bag or pouch having an open top end. After the pouch is filled, the open top end is heat sealed to close the pouch. By virtue of the orientation of the film, the resulting pouch exhibits a linear tear property across its top end. To facilitate the opening of the pouch across its top, one edge of the pouch adjacent the top is slit or nicked to provide a starter tear. Thus, opening of the pouch is accomplished by tearing the top off of the pouch.
While such action may be effective to provide ready access to the interior of the pouch, the tearing away of the top portion of the pouch limits the pouch's utility for being reused and reclosed at its top end.